1. Field of the Invention
The present invention relates to clamping devices, commonly known as pipe clamps that are used to join together the flanged ends of two objects so that a fluid impervious seal is created between the opposing flanges. More particularly, the present invention relates to such clamping devices that are designed to provide a clamping tension that varies with changing conditions.
2. Description of the Prior Art
In the manufacture and processing of pharmaceutical products, dairy products and other materials that require a sanitary processing environment, it is common for materials to be stored and transported in stainless steel containers. Such stainless steel containers are manufactured by Eagle Stainless Container, Inc, of Ivyland Pa. The use of stainless steel is preferred because it enables the containers to be cleaned and sanitized in an autoclave or other harsh washing environment after they have been used. The stainless steel containers can therefore repeatedly be made sterile and can be used over and over again.
Since stainless steel containers are often used to house sterile materials or bioreactive materials, such containers typically do not contain threaded closures. Threaded closures provide confined areas between threads that may harbor contaminants or bioreactive material. Due to the physical shape of the threads, it is very difficult to properly clean threads to the sanitary standards needed. It is for this reason that threaded closures are generally not used. Rather, what is used are flanged caps.
Many stainless steel containers are manufactured with access ports that terminate with a flange connection. The flanged connection is a circular flange that radially extends from the neck of the access port. The access port can therefore be connected to a pipe with a similar flange connection or a cap that contains the proper sized flange connection. To join any two flanged connections together, the two flanges are placed in abutment so that the openings in the center of each of the flanges align. An O-ring or other sealer is placed between the two flanges. The flanges are then clamped together in a manner that compresses the O-ring and prevents the flanges from falling out of alignment.
In the prior art, there are many different types of clamping mechanisms that have been used to join together flanged connections. Typically, the clamps that have been used are annular in shape. Hinges are disposed along the annular structure to enable the annular structure to open. The clamps are opened and then closed over the span of the two adjoining flanges. The presence of the clamping device biases the adjoining flanges together and prevents the adjoining flanges from moving out of their aligned positions.
Prior art clamping devices with a single hinge are exemplified by U.S. Pat. No. 5,018,768 to Palatchy, entitled Pipe Coupling Hinge. Prior art clamping devices with multiple hinges are exemplified by U.S. Pat. No. 4,568,115 to Zimmerly, entitled Multi-Piece Pipe Clamp. Regardless of the number of hinges present, such prior art clamping devices typically contain a rocking bolt assembly that is pivotably connected to one end of the clamp. A wing nut is used to tighten the rocking bolt assembly. The wing nut passes over a slot that is positioned on the opposite end of the clamp. By tightening the wing nut, the diameter of the clamp can be reduced and the clamp can be tightened over the flanged connections.
In many applications, containers undergo severe temperature changes. For instance, a container may be filled at room temperature and then placed in a cryogenic environment, or vise versa. As the temperature of a container changes, the vapor pressure within the container changes and the forces on the cap of the container change. Additionally, as the container is moved into environments of differing temperatures, the temperature of the clamp used to hold a cap onto the container also changes. As a clamp experiences temperature changes, the metal of the clamp either expands or contracts. As such, a clamp that is very tight in one environment may become very loose in a different environment.
A need therefore exists for a new clamp design that is capable of providing a steady clamping pressure regardless of severe changes in temperature. This need is met by the present invention as it is described and claimed below.
The present invention is a clamping device that is used to maintain a consistent clamping pressure on a flanged connection despite changes in temperature and changes in internal pressure behind the flanged connection. The clamping device contains a plurality of arcuate segments. The first and the last of the arcuate segments contain base protrusions that align when the clamping device is closed. One of the base protrusions serves as the housing for a rocking bolt assembly. The rocking bolt assembly includes a threaded rod that joins to a shaft by a pivot. The threaded rod and shaft extend through a hole in the base protrusion. The shaft has an enlarged head that prevents the shaft and the threaded rod from passing through the hole. A wing nut engages the threaded rod and applies tension to both the threaded rod and the shaft. The amount of tension applied by the wing nut varies with changes in temperature. To compensate for variations in wing nut tension, at least one spring is provided around the shaft within the hole of the base protrusion. The spring, or springs, is compressed by the tension applied by the wing nut. When compressed, the spring, or springs, also applies tension to the shaft. The tension applied by the spring, or springs, compensates for any reduction in wing nut tension caused by a change in temperature.